MiR-219a-5p enhances cisplatin sensitivity of human non-small cell lung cancer by targeting FGF9.

Cisplatin (DDP) resistance is a major obstacle in the treatment of non-small cell lung cancer (NSCLC). MicroRNA-219a-5p (miR-219a-5p) has been reported to be a tumor suppressor in several cancers, but whether it regulates chemosensitivity in NSCLC remains unclear. Here, using quantitative real time PCR analysis, we observed that miR-219a-5p was down-regulated in responding tumor tissues compared with that in non-responding tumor tissues from NSCLC patients received DDP-based chemotherapy. Consistently, miR-219a-5p expression was lower in cisplatin (DDP)-resistant NSCLC cell lines (A549-R and SPC-A1-R) than that in corresponding parental cells (A549 and SPC-A1). Gain of-function assay showed ectopic expression of miR-219a-5p reversed DDP chemoresistance of NSCLC cells in vitro and in vivo. Using bioinformatics prediction and dual-luciferase reporter assays, we identified the FGF9 gene as a novel direct target of miR-219a-5p. Moreover, restoration of FGF9 expression reversed the miR-219a-5p-mediated chemosensitivity. In conclusion, this study demonstrated miR-219a-5p plays a crucial role in the development of acquired drug resistance to DDP in NSCLC cells by targeting FGF9 and might be a therapeutic target for DDP resistance in clinical practice.